Various vacuum specimen-sampling containers, wherein sealed containers, the inside being under a reduced atmospheric pressure state, is known. Among such vacuum specimen-sampling containers, for example, vacuum blood-sampling tubes are most generally used. An example of such vacuum blood-sampling tubes is disclosed in Patent Document 1, for instance.
One example of the vacuum blood-sampling system disclosed in Patent Document 1 is shown in FIGS. 21(a) to 21(c). This vacuum blood-sampling system comprises a vacuum blood-sampling container 80 shown in FIG. 21(a), a vacuum blood-sampling holder 83 shown in FIG. 21(b) and a vacuum blood-sampling needle 85 shown in FIG. 21(c). The vacuum blood-sampling container 80 comprises a blood-sampling tube 82 with an opening at an end and a stopper 81 which seals the opening of the blood-sampling tube 82. The stopper 81 is made of an elastic material having a needle-hole sealing property and a gas barrier property. Here, the vacuum blood-sampling holder 83 is designed so that the vacuum blood-sampling container 80 is inserted therein from the opening at an end. A blood-sampling needle holding hole 84 is formed at the other end of the vacuum blood-sampling holder 83, an internal thread is formed in the blood-sampling needle holding hole 84. On the other hand, the vacuum blood-sampling needle 85 has needle tips 87 and 88 at the both ends. A hub 86 on which an external thread portion is formed is formed on the needle tip 87 side. The hub 86 is designed to be screwed into the blood-sampling needle holding hole 84 of the vacuum blood-sampling holder 83 to be secured therein.
FIG. 23 is a schematic perspective view to explain a method of sampling blood by using the vacuum blood-sampling system disclosed in Patent Document 1. Referring to FIGS. 21(a) to (c)and FIG. 23, the blood-sampling step is explained.
In sampling blood, the vacuum blood-sampling needle 85 is threadedly engaged with the blood-sampling needle holding hole 84 of the vacuum blood-sampling holder 83. Next, the vacuum blood-sampling container 80 is inserted into the holder 83, and pushed in such a degree that the needle tip 87 of the vacuum blood-sampling needle 85 does not penetrate the stopper 81, and the needle tip 87 is once sealed. This makes it possible to prevent blood leaking from the needle tip 87, in insertion of the needle tip 88 into a blood vessel. As shown in FIG. 23, while holding the entire structure of the blood-sampling needle 85, the holder 83 and the blood-sampling container 80 coupled to one after another with the hands in a manner so as to align it along the direction of a blood vessel axis, the blood-sampling operator inserts the tip of the needle 88 on the blood-vessel piercing side into a blood vessel. Next, when the blood-sampling container 80 is further pushed into the holder 83, the needle tip 87 penetrates the stopper 81, and blood flows into the blood-sampling container 80 in accordance with a pressure difference between the blood-sampling container side and the blood vessel side. When the pressure difference between the both sides is reduced to zero, the flow of the blood is stopped, and in this state, the entire blood-sampling system is shifted so that the needle tip 88 is drawn from the blood vessel.
The blood-sampling needle 85 is called as a so-called single blood-sampling needle, which is used when the blood sampling is carried out into a single vacuum blood-sampling container. In carrying out the blood sampling into a plurality of blood-sampling containers, this single blood-sampling needle cannot be used. In other words, since, in exchanging blood-sampling containers, the needle tip 88 needs to be kept inserted into the blood vessel, blood is leaked from the needle tip 87 in the case of using the single blood-sampling needle. In contrast, in the case when a multiple blood-sampling needle 89 having a structure shown in FIG. 22 is used, since an elastic sheath 90 is externally inserted to the needle tip 87 on the stopper piercing side, with the needle tip 87 being coated in an air-tight manner, the leak of blood can be prevented.
In the case when such a multiple blood-sampling needle 89 is used, after an assembled body comprising the multiple blood-sampling needle 89 and the holder 83 is prepared, the needle tip 88 of the multiple blood-sampling needle 89 is inserted into a blood vessel. Then, the blood-sampling container 80 is inserted into the holder 83 so that the blood-sampling container 80 is allowed to communicate with the blood vessel.
With respect to a material used for the blood-sampling tube 82 shown in FIG. 21(a), conventionally, glass has been used, however, in recent years, in place of the blood-sampling tube made of glass, a plastic blood-sampling tube made of a thermoplastic resin having a superior gas-barrier property, such as polyethylene terephthalate, has been used in many cases.
With respect to the elastic material used for the stopper 81 shown in FIG. 21(a), since a superior gas-barrier property is required so as to maintain a proper reduced atmospheric pressure degree inside the blood-sampling container, and since a proper needle-hole sealing property after the withdrawal of the needle tip is required, cross-linking isobutylene-isoprene rubber (cross-linking IIR, cross-linking butyl rubber) has been conventionally used. However, the cross-linking rubber requires a long period of time for a curing reaction step and post-steps, such as water-washing and removing steps of a curing reaction agent and elusive substances derived from side products, etc. of the curing reaction, resulting in degradation in the productivity. For this reason, in recent years, stoppers, prepared by using a thermoplastic resin and a thermoplastic elastomer which can be injection-molded, is proposed, for example, in Patent Documents 2 to 7.
After the blood-sampling by using the vacuum blood-sampling system shown in FIGS. 21(a) to (c), in the case when, for example, a biochemical inspection is carried out thereon, carrying out a centrifugal separation after the completion of coagulation of the blood, serum is obtained as a supernatant fluid so that after the stopper 81 is removed, one portion of the serum is taken by using a pipette and the like and various components, such as electrolytes, enzymes and lipids, are subjected to concentration analyses by using an analyzing device. With respect to the residual specimen, the blood-sampling container is again sealed with the stopper 81 for re-inspection, and stored in a cold state or in a frozen state. In this case, however, when, after a blood-sampling container is once opened and a specimen is partially taken for inspections, the container is re-sealed, the inner air of the container is compressed due to the superior sealing property of the stopper to cause an increase in the inner pressure, and the stopper is gradually raised to eventually come off to often cause a problem, that is, a so-called pop-up phenomenon.
Patent Document 8, on the other hand, discloses a stopper for a bottle having a fit-in structure in which a ring-shaped rib, which protrudes on an internal wall surface or on an external wall surface in the vicinity of an open end of a blood-sampling tube made of glass or plastics, is formed and a ring-shaped groove which is engaged with the ring-shaped rib is formed in a rubber stopper. Moreover, Patent Document 10 discloses an opening and closing device for a cylinder-shaped case in which a screw cap and a rubber stopper are combined with each other.
These fit-in structure or screw cap structure provide effective means for preventing the pop-up phenomenon. However, although the blood-sampling tube made of glass may adopt these structures, the blood-sampling tube made of plastics has a difficulty in adopting these structures because the dimension of the protrusion of the ring-shaped rib to be prepared is limited to only a small one which does not impair the releasing property from the metal mold, unless a complex sliding mechanism is incorporated into a molding metal mold, and it becomes difficult to obtain a clear fitting-in effect. Moreover, the screw cap structure requires frequent attaching and detaching operations to consume much labor in repeating the opening and closing operations of a number of blood-sampling tubes. Since polyethylene terephthalate, which has been adopted as a material for blood-sampling tubes made of plastics in recent years, has a comparatively low thermally deforming temperature of about 65° C., the internal diameter of the blood-sampling tube open portion tends to become larger due to a fitting force exerted by the stopper with a lapse of time, easily resulting in the pop-up phenomenon.
In the case when a thermoplastic resin or a thermoplastic elastomer is used as the stopper, the thermoplastic resin and the thermoplastic elastomer are extremely greater in compression permanent strain in comparison with thermosetting elastomers. For this reason, as time elapses after such a stopper was attached to a blood-sampling tube, in particular, when left for a long time under high temperatures in summer, the fitting force between the stopper and the blood-sampling tube is almost lost in a very short time of days. Therefore, in the case when a stopper made of a thermoplastic resin or a thermoplastic elastomer is used in combination with a blood-sampling tube made of polyethylene terephthalate, a problem arises in which the deformation of the blood-sampling tube and the slackening of the stopper due to the compression permanent strain jointly cause further slackening.    Patent Document 1: Japanese Kokai Publication Sho-62-227316    Patent Document 2: Japanese Kokai Publication Sho-57-59536    Patent Document 3: Japanese Kokai Publication Hei-3-97450    Patent Document 4: Japanese Kokai Publication Hei-4-279152    Patent Document 5: Japanese Kokai Publication Hei-7-51253    Patent Document 6: Japanese Kokai Publication Hei-10-201742    Patent Document 7: Japanese Kokai Publication Hei-11-318868    Patent Document 8: Japanese Kokai Publication Sho-58-142256    Patent Document 9: Japanese Kokai Publication Sho-52-112481    Patent Document 10: Japanese Kohyo Publication Hei-3-505320